fork: Using clone_flags for legacy clone check

In the current implementation of clone(), there is a line that
initializes `u64 clone_flags = args->flags` at the top.
This means that there is no longer a need to use args->flags
for the legacy clone check.
Signed-off-by: Wang Jinchao <wangjinchao@xfusion.com>
Link: https://lore.kernel.org/r/202401311054+0800-wangjinchao@xfusion.comSigned-off-by: Christian Brauner <brauner@kernel.org>

kernel/fork.c

@@ -2875,8 +2875,8 @@ pid_t kernel_clone(struct kernel_clone_args *args)
 	 * here has the advantage that we don't need to have a separate helper
 	 * to check for legacy clone().
 	 */
-	if ((args->flags & CLONE_PIDFD) &&
-	    (args->flags & CLONE_PARENT_SETTID) &&
+	if ((clone_flags & CLONE_PIDFD) &&
+	    (clone_flags & CLONE_PARENT_SETTID) &&
 	    (args->pidfd == args->parent_tid))
 		return -EINVAL;